Charles was also approached by a concerned woman in Fishlake, who asked him: "Sir, how is your father?"

Getty

In a statement, the palace said: “The Duke of Edinburgh travelled from Norfolk this morning to the King Edward VII Hospital in London for observation and treatment in relation to a pre-existing condition.

“The admission is a precautionary measure, on the advice of His Royal Highness's doctor.”

According to Mail Online, Philip has also been "battling a flu-like illness for weeks" and suffered a fall before being rushed to hospital.

Speaking about the Duke’s health in recent months, one source told the publication: “The Duke has had a bad turn recently and has been looking much frailer of late.

The Duke was visiting flood-hit communities in South Yorkshire, when a reporter asked him to comment on his father’s condition.

Supplied

“He's a remarkable man who has always prided himself on how robust he is, but he is six months off his 99th birthday and age takes its toll.

“He hasn't been looking terribly well of late,” the royal insider said.

While Prince Charles said that his father was being looked after in hospital, he added that's all he knows.